he following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/chromite/+/907239157e6a16f20a6587c9457af9b0fa144341

commit 907239157e6a16f20a6587c9457af9b0fa144341
Author: Caroline Tice <cmtice@google.com>
Date: Fri Mar 30 23:53:01 2018

Add new builder and builder stages for clang-tidy warnings.

This adds a new waterfall builder, with the appropriate new stages,
for generating clang-tidy warnings for chrome in the build logs,
parsing the build logs to generate warnings.{html,csv} files,
generating a tarball of the warnings files and uploading them to
gs.

BUG=chromium:687243
TEST=In the process of testing.

Change-Id: Id9c161aaaef999125fb454fc2537ea16ceb9ba4b
Reviewed-on: https://chromium-review.googlesource.com/985139
Commit-Ready: Caroline Tice <cmtice@chromium.org>
Tested-by: Caroline Tice <cmtice@chromium.org>
Reviewed-by: Caroline Tice <cmtice@chromium.org>

[add] https://crrev.com/907239157e6a16f20a6587c9457af9b0fa144341/scripts/cros_generate_tidy_warnings.py
[modify] https://crrev.com/907239157e6a16f20a6587c9457af9b0fa144341/cbuildbot/chromeos_config.py
[modify] https://crrev.com/907239157e6a16f20a6587c9457af9b0fa144341/cbuildbot/config_dump.json
[modify] https://crrev.com/907239157e6a16f20a6587c9457af9b0fa144341/cbuildbot/waterfall_layout_dump.txt
[modify] https://crrev.com/907239157e6a16f20a6587c9457af9b0fa144341/cbuildbot/stages/artifact_stages.py
[add] https://crrev.com/907239157e6a16f20a6587c9457af9b0fa144341/cbuildbot/builders/clang_tidy_builders.py